Here's an interesting twist to the debate: what if he's right?
I'm not at all religious, don't believe in the concept of heaven and hell and therefore obviously don't agree with what he says. However, even as a confirmed atheist I couldn't possibly know that I was absolutely, 100% right. It's purely just my personal belief.
So playing devil's advocate (pun intended) for a moment; given none of us can possibly know for certain that he's wrong, should he lose his job for speaking what he believes to be the truth?
If he is right then the Bible prophesies just this: "and he provides that no one will be able to buy or to sell, except the one who has the mark, either the name of the beast or the number of his name."*
* I knew watching The Omen would come in useful one day!